There are a multitude of portable, battery powered electronic devices in existence today. When the batteries in these devices run out of power, a user either has to replace the batteries or recharge them. In the distant past, rechargeable batteries had to be removed from the corresponding device and inserted into a separate battery charger to be recharged. Later, devices were made available that would allow batteries to be charged within the devices themselves by attaching the device to an AC powered transformer or charging station. Further progress was made with devices that would automatically recharge when physically connected to a data port of a larger system (e.g., an MP3 player that recharges when connected to a USB port of a computer). A more recent advance allows portable devices to be recharged wirelessly. As the name implies, wireless charging systems allow portable devices to be charged without the use of a charging cable or physical connection. That is, energy is transferred to the device through the air and, when received, is converted to a form that allows a battery in the device to be charged.
Wireless charging has many benefits. One of the benefits is convenience. That is, a device can be charged without having to physically connect it to a charging structure. Thus, a cell phone can be charged while it sits untethered on a user's desk. For certain types of devices that are difficult or impossible to connect to a wired charging unit, wireless charging is especially valuable (e.g., battery powered medical implants, wearable electronics, etc.). The lack of a need for wired charging structures also has environmental benefits. For example, it has been estimated that wired chargers account for 51,000 tons of waste per year in the United States. Much of this waste can be eliminated with widespread adoption of wireless charging.
There is a need for techniques and systems that are capable of implementing wireless charging in a convenient, reliable, and cost effective manner.